Battery energy storage control systems and methods for a grid tie inverter coupled to a photovoltaic system
A distributed control system uses a central controller in Internet communication with a local controller to manage grid tie attachment with a battery to form an integrated battery energy storage system (BESS). The BESS is capable of charging or discharging the battery, as well as correcting grid phase with volt amp reactive (VAR) leading or lagging operation modes. Examples shown include simple BESS charging and discharging, BESS integrated with renewable energy sources (here photovoltaic), and direct current fast charge (DCFC) connections with an electric vehicle.
1. A battery energy storage system (BESS), the system comprising:
(a) a central controller computer;
(b) a non-transitory memory storing instructions executable by the central computer;
(c) a local controller computer;
(d) a non-transitory memory storing instructions executable by the local computer;
(e) wherein said central controller instructions and said local controller instructions, when respectively executed by the central controller computer and the local controller computer allow for a communications interface configured for network communications therebetween;
(f) a control system computer comprising the local controller computer and the central controller computer;
(g) a grid tie inverter, comprising:
(1) a port for connection to an electrical grid;
(2) a port for connection to a battery; and
(3) a communications interface configured for communications with the control system;
(h) wherein said central controller and said local controller instructions, when executed among the local controller computer and the central controller memory, form a set of operational instructions performing steps comprising:
(1) controlling communication between the central controller computer and the local controller computer;
(2) executing a safety features control section; and
(3) executing an operation control and monitoring section; and
(i) a second grid tie inverter, the second grid tie inverter comprising:
(1) a second port for connection to an electrical grid;
(2) a second port for connection to a photovoltaic system; and
(3) a second communications interface configured for communications with the control system; and
wherein the set of operational instructions further performs steps comprising:
(1) collecting an historical power series;
(2) decompositing the historical power series into a constitutive series through wavelet transformations;
(3) modeling each of the constitutive series by a plurality of Auto-Regressive Moving Average (ARMA) models for recognition of their linear patterns, whereby a plurality of ARMA models are produced;
(4) recompositing an estimated series obtained from the plurality of ARMA models for each constitutive series through an inverse wavelet transform; and
(5) compensating for an error of the wavelet transformation and ARMA model predictions by recurrent neural networks through capturing of nonlinear patterns buried in a difference between the historical power series and the estimated series, whereby a time series estimate is produced.
2. The battery energy storage system (BESS) of claim 1 , wherein the control system computer is configured to monitor and control criteria for the safe operation of the battery.
3. The battery energy storage system (BESS) of claim 2 , wherein the monitor and control criteria for the safe operation of the battery are selected from the group of criteria consisting of:
(a) detecting battery over-temperature;
(b) detecting battery overcurrent charging;
(c) detecting battery overcurrent discharging;
(d) detecting battery undervoltage;
(e) detecting battery overvoltage;
(f) detecting battery ventilation control;
(g) detecting battery ventilation fault;
(h) detecting battery cell imbalance;
(i) detecting degraded battery state of health;
(j) detecting battery short circuit;
(k) detecting arc fault; and
(l) detecting ground fault.
4. The battery energy storage system (BESS) of claim 1 , wherein the control system computer is configured to monitor and control criteria for the safe operation of the grid.
5. The battery energy storage system (BESS) of claim 4 , wherein the monitor and control criteria for the safe operation of the grid are selected from the group of criteria consisting of:
(a) monitoring and controlling of the BESS in real time;
(b) providing grid support by leveling loads on the electrical grid;
(c) regulating electrical grid voltage;
(d) improving power quality of the electrical grid;
(e) improving transient and phase stability of the electrical grid;
(f) compensating for unbalanced loads on the electrical grid; and
(g) providing spinning reserves for the grid.
6. The battery energy storage system (BESS) of claim 1 , wherein said set of operational instructions are configured to manage system operational modes selected from the group consisting of: a battery charging mode, a battery discharging mode, a current leading mode, and a current lagging mode.